attenuated retinal vessels

Night blindness is an early symptom which may be noted in early childhood.  Vision loss can be documented in early childhood and progressively worsens to hand motions or light perception by the 3rd to 5th generation.  The fundus appearance has been described as normal in 1-year old patients but retinal pigmentary changes and arteriolar changes are evident in some children by the age of 2 years.  Typical bone spicule pigmentary changes have been described in some older patients.  Staring at lights (photophilia) has been noted in children under 1 year of age while eye-rubbing (oculodigital sign) may be seen soon thereafter.  Nystagmus is often present.

ERG responses are greatly diminished or nonrecordable.  Rods are more severely affected than cones.  OCT shows loss of inner and outer segments of photoreceptors.

The onset of nyctalopia apparently varies from early childhood to 20 years of age and is usually the presenting symptom.  The loss of acuity is progressive (20/30 to 20/400) with older patients generally having more severe loss but there is little direct correlation with age.  Peripheral fields are progressively constricted, ranging from 10 to 30 degrees.  Some patients develop posterior subcapsular cataracts.  Retinal pigmentation is often mottled but 'bone spicules' are seen in about half of individuals.  Retinal vessels are narrowed.  The ERG shows generalized rod-cone dystrophy.

Patients note reduced vision in brightly-lit environments with onset in early adulthood and progressive central vision loss thereafter.   Nystagmus, photophobia, and dyschromatopsia may be present.  Younger individuals may complain of night blindness.  Visual fields show diffuse progressive suppression with relative sparing of selected areas such as the peripapillary region.  The ERG documents primary cone dystrophy but less involvement of the rods.  EOG testing in 4 patients showed reduced light-dark ratios.  Macular degeneration, attenuated vessels, subtle salt-and-pepper pigmentation, and spicular pigmentary deposits in the mid-periphery may be seen.

Onset of night blindness occurs early in the second decade of life.  Vision is in the range of 20/40 to 20/100 in the first decades worsens slowly but there is a wide range.  Some older individuals may have hand motion vision in at least one eye but some retain 20/40.  All patients have peripheral field restrictions and some have pallor of the optic disc.  Retinal vessels are attenuated.  Fundus pigmentation is usually abnormal with some combination of bone spicule and diffuse salt and pepper pigmentation.  The macula is usually involved with a flat fovea, cystoid macular edema, and chorioretinal atrophy.

Retinal thinning is seen on OCT.  The ERG can be flat but in some individuals the rod responses are primarily reduced.

There is considerable clinical heterogeneity with a wide range in age of onset and progression.  Night blindness, sometimes with photophobia, has its onset in the second or third decade of life and central acuity can be impacted by age 30 years.  Other patients have no symptoms until the fifth decade.  Some patients lose the ability to perceive light by the sixth decade.  The visual fields are usually constricted although one patient had a central scotoma.  The ERG is usually nonrecordable but other patients may have a variable rod-cone pattern of attenuation.  The retinal vessels are also attenuated and some patients have mild optic atrophy.  The pigmentary retinopathy is also variable with sometimes central lesions and in other patients more peripheral.  One patient had posterior subcapsular cataracts.

High myopia and marked nystagmus are cardinal ocular findings.  Night blindness leads to symptoms between 2 and 4 years of age.  Vision loss leads to complete blindness by age 15 to 18.  Visual acuity in young adults is often 20/400 to NLP.  Cataracts with subluxated lenses, glaucoma, and chorioretinal atrophy are often present.  Scattered pigment clumping, attenuation of the retinal vasculature, and prominent choroidal vessels can often be seen.  Marked optic atrophy is usually present.  Phthisis and band keratopathy may be seen in older individuals although no retinal detachments have been reported.  The vitreous is described as degenerated in several patients and a vitreal hemorrhage was seen in one patient.

Persistent optic nerve edema is eventually followed by some degree of optic atrophy.  The nerve edema may be seen early in the first decade of life and is not associated with increased lumbar puncture pressure.  Peripapillary hemorrhages may be seen.  Visual acuity may decrease somewhat by the end of the first decade of life and becomes functionally significant in early adolescence and may be reduced to counting fingers.  The ERG, which shows minimal dysfunction early, eventually appears nearly flat without photopic or scotopic responses.  The retinal vessels become markedly attenuated and the macula may be mildly edematous and show pigmentary changes.  Pigment clumping is not seen.  Visual fields show a central or cecocentral scotoma, enlargement of the blind spot, and eventually severe peripheral constriction.  The vitreous and aqueous humor sometimes have an increased number of cells.   Lenticular opacities requiring cataract surgery has been reported.  One patient developed a phacomorphic angle closure attack at the age of 19 years.